Electric discharge device



Oct. 12 1926. 1,603,087

e. M. J. MACKAY ELECTRIC DISCHARGE DEVICE Filed Oct. 1, 1920 Inventor:

Geor e TTLJ. mackay His Attorney.

Patented Oct. 12, 1926.

- UNITED-STATES PATENT OFFICE.

crease in. J. mAcKAY, or sonnnnc'mnr, NEW mm, assronon 'ro oEnnRAL EL-Ectrmc comm. A CORPORATION (IF-NEW YORK.

mnc'rmc 'mscnanen nEvIoE.

Application filed October 1, 1920. Serial No. 414,099.

. ductor. Such a lamp is described in my prior application Serial No. 354,195, filed- Jan. 26, 1920. a

'It has been found that in the operation of a lamp of this type with direct current, a wasting away occurs at the cathode end of the filament. I have found that this loss of metal is not due to cathbdicis'puttering, but appears to be dueto excessively high temperature of the cathode end. This section ofa the filament carries what may be termed two electric currents, namely, a current passing through-the filament and a current passing from one section of the filament" to another, as will be hereinafter more fully explained. When the filament is heated by alternating current, both terminals tend to waste away as they alternately act as cathode;

In accordance with my present invention, I have provided a device in which the filament is arranged to carry both an electron or discharge current and a resistance heating current without local disintegration;

In the accompanying drawing, Fig. 1 11- lustrates a lamp embodyingmy invention; and Fig. 2 is a'detail view of one section of the filament shown in Fig. 1.

The lamp shown in Fig. 1 consists of a sealed bulb 1 into the stem 2 of which are sealed the current supply conductors 3, 4. A spiral filament 5 isconductively joined at its end to the conductors 3 4. A support 6 embedded in the stem 2 are at its extremity a button 7 into which are sealed hooks 8 serving as intermediate support for the filament 5. The bulb contains an ionizable vapor, for example, a quantity of alkali metal such as sodium, or a suitable gas. for example, neon at a ress'ure of about ten microns, which is too ow to carry away heat to an a preciable extent. My invention is not limited in application to a device in which a gas or vapor takes part in the conduction of current. The benefits of my invention may be obtained in a device in which an electron discharge occurs between parts of a conductor independently of gas ionization.

The filament 5, which has a substantially uniform cross section, consists of a plurality of sections arranged in zigzag form. As will appear more clearly in Fig. 2, the spiral is opened adjacent thev terminals, the pitch of the spiral "gradually decreasing from a nearly straight section adjacent the lead 3 to a closely. wound spiral adjacent the short link 9,connecting adjacent sections of the filament.

At the operating temperature, say, at 2200 C. a current passes through the gaseous fillin in the bulb between parts of the filament avin suflicient difference of potent al to pro uce a discharge resultingin luminosity.

During one current Wave the current passes from the negative end of the filament, say, the end adjacent the lead wire 3 to the more positive portions-of the filament as Well as the lead wlre 4. Theparts most remote from the negative end receive the greatest part of the discharge current due to the greater otential difference. In other words the disc large passes from a given surface at the cathode end of the filament to "other more positive parts in proportion to their potent al difi'erence. In the case of the alternating current device illustrated this action is reversed each half wave. In consequence the outermost filament sections carry more current and operate at a higher temtpliarature than the intermediate part of the ament. As the current through the gas gadually decreases to oints more remote om the leads, only t e heating current gasses-through the intermediate parts of the ament. By a proper adjustment of pitch as described, the filament .will operate at a uniform temperature, the greater heating crating temperature of said device a gaseous pressure suliicicntlv high to be capable of carrying an appreciable current by ionization but too low to convey heat to a substantial degree. and a filamentary conductor operating at incandcscence mounted in said envelope, and current-conveying terminals therefor, said conductor having a substan-,

tially uniform cross-section and being arranged to have a greater heat dissipatmg capacity adjacent the negative terminal than at an intermediate portion. 2., The combination of velope, a quantity of sodiumthere'in, a 'con-' ductor operating at incandescenceinsa id envelo e, said conductor haying part 'at fie form of a spiral Wlt-h a pitch pro-z least t gressively decreasing from the negatlve terminal towards a more positive"part"of the an enclosed en-j r c'ondnctor.

ing at y the operatin temperature 0f the lamp a pressureof t eorder bf magnitude of about ten microns of mercury, a coiled conductor therein which .is. ca 'iablev ofopcrating at incandescence, and electric terminal conductorstherefor, the coils of said conductor rad'acent the negative terminal being spaced arther apart to cause the heat dissipating capacity ,9? said coils to be greater than an adjolnmgportlon of said T In witness whereof, I have hereunto set my hand this 30th day of September, 1920. GEORGE M. J. MACKAY. 

